Acoustic distributor

ABSTRACT

An acoustic distributor in which a cylindrical enclosure, constructed to provide extreme attenuation of sound passing through the walls thereof, contains a radio-type loudspeaker. The enclosure has a plurality of peripherally located and spaced acoustic ports to which individual acoustic headsets may be coupled to that sound generated within the enclosure is propagated by way of the listening tubes of the acoustic headsets to several listeners. Each of the headsets may be individually connected and disconnected from the distributor without interfering with the sound transmission to other headsets and each acoustic port is provided with a slide valve mechanism mounted exteriorly of the soundproof enclosure and arranged to be easily and substantially automatically opened as a consequence of the motion employed in coupling a listening tube to the associated acoustic port.

United States Patent [1 1 Malmrose et al.

[451 Nov. 5, 1974 ACOUSTIC DISTRIBUTOR [75] Inventors: Gerald E.Malmrose, Chatsworth; Ulf R. Helgesson, Woodland Hills, both of Calif.

[73] Assignee: Acoustifone Corporation,

Chatsworth, Calif.

22 Filed: June 25, 1973 21 Appl. No.: 372,798

[56] References Cited UNITED STATES PATENTS 3,353,625 11/1967 Scanlon..181/31B Primary Examiner-Stephen .l. Tomsky Attorney, Agent, orFirm-Benjamin Dewitt [57] ABSTRACT An acoustic distributor in which acylindrical enclosure, constructed to provide extreme attenuation ofsound passing through the walls thereof, contains a radio-typeloudspeaker. The enclosure has a plurality of peripherally located andspaced acoustic ports to which individual acoustic headsets may becoupled to that sound generated within the enclosure is propagated byway of the listening tubes of the acoustic headsets to severallisteners. Each of the headsets may be individually connected anddisconnected from the distributor without interfering with the soundtransmission to other headsets and each acoustic port is provided with aslide valve mechanism mounted exteriorly of the soundproof enclosure andarranged to be easily and substantially automatically opened as aconsequence of the motion employed in coupling a listening tube to theassociated acoustic port.

10 Claims, 10 Drawing Figures nuv 5:914 3.8458 8 PATENTED sum 10F 3 3Background of the Invention This invention relates to sound distributionapparatus and more particularly to a' reliable, rugged and economicallymanufacturable acoustic distributor of the type used for distributingsound froma single electroaccoustic transducer to a plurality oflisteners without disturbing other nearby persons.

One problem encounted in the development of practical acousticdistributors for classroom use has been the difficulty of achieving anadequate sound level at the ears of all listeners while at the same timekeeping sound leakage at a low enough level to preclude disturbance ofnearby persons engaged in other activities. In the prior art oneapproach has been to provide each listener or student with a headsetwhich includes a pair of electrically energized transducers. Suchsystems are disadvantageous for use in primary school classrooms in thatthe relatively fragile electric headsets must be entrusted to smallchildren. Additionally, while such electric headsets do not actuallycarry dangerous voltages it has been found that educational systemadministrators are generally quite reluctant to permit unsupervised useof electrically wired headsets in primary school classrooms Anadditional factor which militates against the use of such prior artsystems is the relatively high cost of maintenance associated withproviding individual electric headsets to a large group of listeners.

In the recent development of audio-visual equipment for use inclassrooms, libraries, hospitals, etc., the trendhas been away from theuse of electrical headsets to the use of acoustic distributors andacoustic headsets which include an elongated hollow listening tubehaving a rigid probe at its input end which can be coupled Summary ofthe Invention In accordance with a preferred form of the presentinvention, the foregoing objects are achieved by an arrangement in whicheach listener is provided with an acoustic headset which includes alistening tube having at its sound input end a rigid probe for couplingto one of the acoustic ports of an acoustic distributing unit. Theacoustic distributor is a thick-walled enclosure, preferablycylindrically in form constructed to provide extreme attenuation ofsound passing through the walls thereof and having a radio-type speakersupported therein. Around the periphery of the enclosure are spaced aplurality of sound output ports through which sound waves generatedwithin the enclosure are propagated to the individual acoustic headsets.Each acoustic port has associated therewith a slide-valve mechanismmounted exteriorly of the soundproof enclosure and operable from aclosed position to an open position when the rigid probe of a headset isinserted into the associated port. The slide-valve mechanism tends tohold the headset probe in place in the acoustic port by applying forceperpendicular to the probe so that inadto one of a plurality of acousticports in the distributor.

In these acoustic distribution systems, it is important that sound bedelivered to the several listeners at substantially equal intensitieswhile limiting the leakage of sound energy to avoid interference withthe activities of nearby non-listeners and thereby permit several groupsof students to be engaged in different activites in a single room. Toinvite and encouragethe use of such apparatus by primary schoolchildren, it is most important that the acoustic distributor be arrangedfor easy and unattended use by small children.

Accordingly, it is a primary object of this invention to provide animproved apparatus for distributing sound to a plurality of listenerswhile maintainingthe sound level to which non-listeners in the immediatearea are subjected at a relatively very low level.

It is a further object of the present invention to provide areliable,rugged and economically manufactur able acoustic distributor having aplurality of acoustic ports for connection of acoustic headsets andhaving an acoustic valve mechanism. positioned adjacent each portoutside the soundproof enclosure and arranged for I facile andsubstantially unattended usage by children in the 3 to 10 year agegroup.

It is an additional object to provide an acoustic distributor havingslide valve mechanisms which operate to automatically grip and hold theheadset probe in the inserted position so that inadvertent disconnectionof the headset from the distributor is substantially avoided.

vertent dislodgment is avoided. Further, each slidevalve automaticallycloses upon intentional removal of the probe so that sound leakage fromthe enclosure by way of acoustic ports which are not in use issubstantially avoided.

Brief Description of the Drawings FIG. 1 is an exploded side viewillustrating the major parts of an improved acoustic distributor inaccordance with the invention; I

FIG. 2 illustrates a cross-section of the speaker supporting. gasket;

FIG. 3 is a top view of the manifold component of the assembly shown inFIG. 1;

FIG. 4 illustrates a cross-section of the manifold taken along the lines4-4 of FIG. 3;

FIG. 5 is a bottom view of the manifold component;

FIG. 6 is a bottom end view of the top component of Description of thePreferred Embodiment The foregoing and other features of the presentinvention will be better understood by consideration of the followingdetailed description of one specific acoustic distributor constructed inaccordance with the invention. As shown in FIG. 1 the acousticdistributor assembly includes a thick-walled top member 13, a radio-typelounspeaker 20, an acoustic manifold 32, and a base member 27 all ofwhich are generally cylindrical in form. For clarity, the valvemechanisms associated with each acoustic port 34 of the manifold havebeen omitted from FIG. 1 but are shown in detail in FIG. 8

and will be described more particularly in the discussion of thestructure shown in FIG. 8.

The major components 13, 20, 27 and 32 as shown in FIG. 1 are assembledtogether by moving the manifold 32 downwardly until it nests within thebase member 27, and by securing the speaker 20 including its peripheralsealing ring or gasket 21 between the upper surface of the manifold 20and the lower surface 18 of the top member 13. The generally cylindricaltop member 13 has a plurality of peripherally spaced flutes or grooves17 which cooperate with the slide-wave mechanisms (in a manner to bedescribed hereinafter) to enhance the facility with which thedistributor can be used. In cross-section, as shown in FIG. 7, the topmember 13 has the form of a truncated cone with a slightly curved topsurface 19, relatively very thick walls 61, and a fairly large internalcavity for accommodating the backside of the speaker 20. The speaker 20conventionally includes an electrical signal input cord which extendsoutwardly through a hole in one side wall of the top member 13 and maybe connected to a source of audio frequency signals such as a taperecorder/player. The sealing ring or gasket 21 which encompasses theperiphery of the speaker has an internal groove 22 which snaps over theperipheral edge of the speaker. When the gasket 21 is clamped betweenthe manifold 32 and the top member 13, it not only seals the enclosureto avoid sound leakage to the surrounding area but also minimizes soundconduction from the speaker rim to the side walls of the othercomponents. That is, the sealing ring or gasket 21 seals the junctionline between members 13 and 32 to avoid sound transmission therethrough,and also resiliently suspends the speaker 20 to avoid sound conductiondirectly from the rim of the speaker to the solid walls of theenclosure. To that end, the gasket 21 is preferably formed of a verysoft and resilient vinyl polymer. The several components as describedabove are secured together by self-tapping screws which extend upwardlyfrom the bottom surface 28 of the base member through appropriate holes39 in the manifold (FIG. 4) to engage aligned apertures 65 in the topmember.

As best shown in FIGS. 3, 4 and 5, the acoustic manifold 32 is agenerally cylindrical structure having a central dome 40 which faces thefront of the loudspeaker 20 and functions in cooperation with annularV-shaped groove 41 to provide a shaped acoustic chamber for directinghigh intensity sound waves from the speaker to all of the twelveacoustic ports 34. The acoustic ports 34 are equiangularly spaced aroundthe periphery of p the manifold and extend horizontally outward from theannular groove 41 through the side walls 42. Each acoustic port 34 iscentered within a vertically tapered surface 37 located between a pairof spaced ribs 36. As best shown in FIGS. 4 and 5, the outer surfaces ofthe ribs 36 are vertical while the surface 37 between each pair of ribsis tapered downwardly so that when the manifold is assembled within thebase member 27, each pair of ribs forms, in conjunction with thecylindrical outer wall 29 of the base, a pyramidal space for containingone of the slide-valve mechanisms.

As shown in FIG. 8, the manifold 32 nests within the base member 27 withits bottom surface resting on the flat bottom 28 of the base member andwith the outer surfaces of ribs 36 disposed in interfacing adjacencywith the inside surface of the sidewalls 29. Aligned with each acousticport 34 is a vertical slot 30 in the side wall 29 of the base member.Each slot 30 is further aligned with one of the vertical grooves 17 sothat each groove 17 and the aligned slot 30 cooperate to provide aguideway for directing the rigid probe 26 of a headset 24 into theassociated acoustic port 34.

Within the pyramidal cavity between adjacent ribs 36 there is containeda slide-valve mechanism comprised of a slider 71, a small diametercompression spring 80 and a spring supporting pin 82 which is formed asan integral part of the base member 27 and extends vertically upwardinto a re-entrant cavity 79 in the bottom of the slider 71. When viewedfrom the side as shown in FIG. 9, the slider 71 is substantiallyrectangular and has first and second planar outer surfaces 73 and 75with the surfaces 73 and 75 being at an angle of about 7 so that anexterior shoulder is formed along the line 76. This shoulder 76 restsagainst the interior surface of the base member side wall 29 so that theslider 71 is free to pivot about an axis formed by the shoulder 76whereby the inner planar surface 78 of the slider is free to pivotallyadjust itselt to closely contact the tapered surface 37 above and belowthe port 34. By this arrangement the slider 71 although mountedexteriorly of the soundproof enclosure is held closely adjacent to andis capable of sealing the port 34 (when the particular port is not inuse) so that sound leakage outwardly from the distributor is reduced toa level of the order of 60 decibels below the internal sound intensitylevel.

The several components of the acoustic distributor preferably are formedby molding from polymeric ma terials. More specifically, the base member27 is preferably made of acrylonitrile-butadienestyrene; the top member13 and the manifold 32 are formed of general purpose woodflour filledphenolic resin; and the sliders 71 are made from a medium-soft (70shore) vinyl polymer.

It is to be emphasized that the structural arrangement of theslide-valve mechanisms is particularly advantageous in that theinsertion and removal of headset probes 26 from the several acousticports 34 is very easy and uncomplicated so that even the smallestprimary school children tend to be invited and encouraged to use theapparatus. The ease of usage is attributable, in part, to thearrangement in which the slidevalve mechanisms are mounted exteriorly ofthe soundproof enclosure to function in cooperation with the probeguideways formed by the grooves 17 and the slots 30. That is, alistening tube probe 26 may be connected to the distributor by simplypushing the end of the probe 26 downwardly along one of the grooves 17whereby it engages the curved upper surface 77 of the slider 71, theslider 71 is moved down and the probe,

in substantially the same motion, enters the acoustic port 34. In FIG.8, reference numberal 86 indicates one of the slide-valves in thedownwardly pressed or open position. The slide valve arrangementprovides the additional and important advantage that when the probe 26is positioned within the acoustic port 34, the associated slider 71maintains a modest pressure against the bottom surface of the probe sothat the of distributors employing poppet-type spring loaded valves,which tend to expel the listening tube probe from the acoustic port, ithas been found that inadvertent pulling on the listening tube, by asmall child, frequently results in the probe being expelled from itsport. This inadvertent disconnection tends to discourage small childrenfrom using the apparatus.

. In the economical manufacture of apparatus of the type described, itis most desirable that the manufacturing tolerances be substantial. Theslide-valves 71 permit relaxed manufacturing tolerances in the sensethat the probes 26 are not required to be precision manufactured forclose-tolerance fit within the acoustic ports 34. A further advantage ofusing slide-valves rather than poppet-type valves is the fact theyprovide positive sound coupling. That is, with the slide-valvemechanisms a student cannot have his headset physically attached to thedistributor without the slide-valve being fully opened. This enables theteacher to verify at a glance that the particular student is receivingsound at his headset. In contrast, with the use of poppet-type valves itis possible for a child to insert his headset probe loosely into anacoustic port without opening the associated valve and, in the absenceof closesupervision, it may be some time before the teacher becomesaware that the particular headset is not receiving sound.

While the present invention has been shown and described in one exemplarform only, it will be obvious to those skilled in the art that it is notso limited but is susceptible to various changes and modificationswithout departing from the spirit and scope thereof.

We claim:

1. ln an acousticdistributor for use in classrooms and the like fortransmitting sound waves from a single electro-acoustic transducer to aplurality of listeners without disturbing other nearby persons:

a substantially cylindrical thick-walled enclosure formed of soundabsorbing polymeric material and having an interior-to-exteriorattenuation characteristic for audio frequency acoustic waves of theorder of about 60 decibels; loudspeaker mounted within said enclosureandadapted to be electrically connected to a source of audio frequencysignals for producing high intensity acoustic waves within saidenclosure;

a plurality of angularly spaced substantially cylindrical aperturesextending radially outward through the walls of said enclosure in asingle horizontal .plane spaced in front of said loudspeaker wherebysound waves of substantially equal intensity are propagated toward allsaid apertures;

a plurality of acoustic headsets, each including an elongated listeningtube having at its input end a semi-rigid probe adapted to be insertedinto any one of said apertures, for conducting sound waves from said oneaperture to the person using the particular headset;

a plurality of valve mechanisms mounted exteriorly of said thick-walledenclosure, respectively adjacent the outer ends of different ones ofsaid apertures;

with each valve mechanism being operable, in a direction substantiallynormal to the longitudinal axis of the adjacent aperture, from itsclosed position to its open position upon, and as a direct consequenceof, the insertion of a listening tube probe into the associated apertureand being operative to exert a retaining force on the inserted probewhereby the probability of inadvertent disconnection of the headsetlistening tube from the enclosure is substantially reduced.

2. An acoustic distributor comprising:

a thick-walled enclosure substantially impervious .to

sound waves;

a speaker mounted within said enclosure and adapted to be coupled to asource of audio frequency electrical signals for producing highintensity sound waves within said enclosure;

a plurality of sound conducting ports extending through the walls ofsaid enclosure from an interior sound chamber adjacent the front of saidspeaker to the exterior of said enclosure; and

slide-valve means mounted exteriorly of said enclosure adjacent eachport and slidably operable, in a direction substantially normal to theaxis of the adjacent port, from a closed position to an open positionand vice-versa whereby sound leakage from said enclosure by way of portsnot having listening tubes coupled thereto is substantially avoided.

3. An acoustic distributor in accordance with claim 2 in which:

said enclosure comprises a substantially cylindrical manifold portionwith said sound-conducting ports extending radially through the sidewalls of said manifold portion and being angularly spaced therearound ina single horizontal plane.

4. The acoustic distributor of claim 2 wherein each slide valve meanscomprises (a) a slide valve element which is reciprocally movable in adirection substantially normal to the port with which it is associated,and (b) spring means for resiliently biasing said element toward theclosed position and contiguously adjacent and covering the exterior endof the port associated therewith.

5. The acoustic distributor of claim 4 wherein each slide-valve elementis formed of a relatively soft and resilient polymeric material and hasa wedge-like configuration withthe thicker portion below the associatedport so that when the wedge-like valve element is moved upwardly by' itsassociated biasing means, it wedges between the outer surface of theenclosure side wall and a peripherally encompassing base member tothereby substantially seal the associated port against undesired soundleakage.

6. The acoustic distributor of claim 4 wherein each of said ports isadapted to receive a hollow semi-rigid probe carried at one end of aheadset listening tube and wherein each slide valve element is formed ofa relatively soft and resilient polymeric material and has a wedge-shapeconfiguration, with the slide valve element being contacted by saidrigid probe and moved from the closed position to the open position uponinsertion of the rigid probe into the associated port.

7. The acoustic distributor of claim 3 wherein said enclosure provides asound intensity differential of the order of decibels between theinterior and the exterior thereof and wherein said slide-valve meanscomprises a plurality of wedge-shaped slide valve elements angularlyspaced around the exterior of said enclosure, respectively overlying theouter ends of said ports, and eavhmovable downwardly to accommodateinsertion of a listening tube probe into its associated port.

8. An acoustic distributor in accordance with claim '4 and furtherincluding a plurality of sound tube headsets for respectively conductingsound from said enclosure to a plurality of individual listeners;

. the walls of said enclosure in a single horizontal plane spaced infront of said speaker whereby sound waves of substantially equalintensity are propagated toward all said ports.

10. An acoustic distributor in accordance with claim 2 in which saidenclosure comprises a. a substantially cylindrical manifold memberhaving a planar top surface on the peripherythereof,

b. a substantially bowl-shaped top member having a bottom surfacecontiguously engaging the top surface of said manifold member, and

c. a sealing ring formed of a resilient polymeric material clampedbetween the bottom surface of said top member and the top surface ofsaid'manifold member, with said sealing ring having aninternal groovewhich engages the peripheral rim of the speaker for supporting thespeaker in a horizontal plane within said enclosure in a manner suchthat sound conduction from the rim of the speaker to the solid walls ofsaid enclosure is substantially obviated.

1. In an acoustic distributor for use in classrooms and the like fortransmitting sound waves from a single electro-acoustic transducer to aplurality of listeners without disturbing other nearby persons: asubstantially cylindrical thick-walled enclosure formed of soundabsorbing polymeric material and having an interior-toexteriorattenuation characteristic for audio frequency acoustic waves of theorder of about 60 decibels; a loudspeaker mounted within said enclosureand adapted to be electrically connected to a source of audio frequencysignals for producing high intensity acoustic waves within saidenclosure; a plurality of angularly spaced substantially cylindricalapertures extending radially outward through the walls of said enclosurein a single horizontal plane spaced in front of said loudspeaker wherebysound waves of substantially equal intensity are propagated toward allsaid apertures; a plurality of acoustic headsets, each including anelongated listening tube having at its input end a semi-rigid probeadapted to be inserted into any one of said apertures, for conductingsound waves from said one aperture to the person using the particularheadset; a plurality of valve mechanisms mounted exteriorly of saidthick-walled enclosure, respectively adjacent the outer ends ofdifferent ones of said apertures; with each valve mechanism beingoperable, in a direction substantially normal to the longitudinal axisof the adjacent aperture, from its closed position to its open positionupon, and as a direct consequence of, the insertion of a listening tubeprobe into the associated aperture and being operative to exert aretaining force on the inserted probe whereby the probability ofinadvertent disconnection of the headset listening tube from theenclosure is substantially reduced.
 2. An acoustic distributorcomprising: a thick-walled enclosure substantially impervious to soundwaves; a speaker mounted within said enclosure and adapted to be coupledto a source of audio frequency electrical signals for producing highintensity sound waves within said enclosure; a plurality of soundconducting ports extending through the walls of said enclosure from aninterior sound chamber adjacent the front of said speaker to theexterior of said enclosure; and slide-valve means mounted exteriorly ofsaid enclosure adjacent each port and slidably operable, in a directionsubstantially normal to the axis of the adjacent port, from a closedposition to an open position and vice-versa whereby sound leakage fromsaid enclosure by way of ports not having listening tubes coupledthereto is substantially avoided.
 3. An acoustic distributor inaccordance with claim 2 in which: said enclosure comprises asubstantially cylindrical manifold portion with said sound-conductingports extending radially through the side walls of said manifold portionand being angularly spaced therearound in a single horizontal plane. 4.The acoustic distributor of claim 2 wherein each slide valve meanscomprises (a) a slide valve element which is reciprocally movable in adirection substantially normal to the port with which it is associated,and (b) spring means for resiliently biasing said element toward theclosed position and contiguously adjacent and covering the exterior endof the port associated therewith.
 5. The acoustic distributor of claim 4wherein each slide-valve element is formed of a relatively soft andresilient polymeriC material and has a wedge-like configuration with thethicker portion below the associated port so that when the wedge-likevalve element is moved upwardly by its associated biasing means, itwedges between the outer surface of the enclosure side wall and aperipherally encompassing base member to thereby substantially seal theassociated port against undesired sound leakage.
 6. The acousticdistributor of claim 4 wherein each of said ports is adapted to receivea hollow semi-rigid probe carried at one end of a headset listening tubeand wherein each slide valve element is formed of a relatively soft andresilient polymeric material and has a wedge-shape configuration, withthe slide valve element being contacted by said rigid probe and movedfrom the closed position to the open position upon insertion of therigid probe into the associated port.
 7. The acoustic distributor ofclaim 3 wherein said enclosure provides a sound intensity differentialof the order of 60 decibels between the interior and the exteriorthereof and wherein said slide-valve means comprises a plurality ofwedge-shaped slide valve elements angularly spaced around the exteriorof said enclosure, respectively overlying the outer ends of said ports,and eavh movable downwardly to accommodate insertion of a listening tubeprobe into its associated port.
 8. An acoustic distributor in accordancewith claim 4 and further including a plurality of sound tube headsetsfor respectively conducting sound from said enclosure to a plurality ofindividual listeners; with each of said headsets having a rigid probecarried at the input end of its sound tube and adapted for sliding theassociated slide valve element from the closed condition to the opencondition when said probe is inserted into one of the ports of saidenclosure.
 9. An acoustic distributor in accordance with claim 2 inwhich said speaker is mounted in a horizontal plane within saidenclosure and in which said ports are angularly spaced around and extendradially through the walls of said enclosure in a single horizontalplane spaced in front of said speaker whereby sound waves ofsubstantially equal intensity are propagated toward all said ports. 10.An acoustic distributor in accordance with claim 2 in which saidenclosure comprises a. a substantially cylindrical manifold memberhaving a planar top surface on the periphery thereof, b. a substantiallybowl-shaped top member having a bottom surface contiguously engaging thetop surface of said manifold member, and c. a sealing ring formed of aresilient polymeric material clamped between the bottom surface of saidtop member and the top surface of said manifold member, with saidsealing ring having an internal groove which engages the peripheral rimof the speaker for supporting the speaker in a horizontal plane withinsaid enclosure in a manner such that sound conduction from the rim ofthe speaker to the solid walls of said enclosure is substantiallyobviated.